Due to environmental pollution, energy crisis and other problems are increasingly serious, and more and more countries around the world have paid attention to the development of energy-saving and environmental-friendly automobiles. An electric automobile as an automobile with almost zero emission becomes a new favorite in the automotive industry, and has been rapidly developed in recent years. Because of inherent advantages, the electric automobile has great development potential.
At the present stage, since technical bottleneck problems of poor motor heat dissipation, extremely large unsprung mass and the like in an electric automobile driven by a wheel hub motor are not solved, the electric automobile is generally driven to run by adopting a power assembly composed of a single motor and a drive axle or a power assembly composed of the single motor, a transmission and the drive axle. Therefore, most of the power assemblies of existing electric automobiles include the drive axle.
Generally, the drive axle in the electric automobile is similar to a drive axle in a traditional internal combustion engine automobile and only plays the role of reducing speed and increasing a torque; and the torque of the motor is amplified and transmitted onto wheels to drive the automobile to run. Therefore, because of a “differential without differential torque” principle in a traditional differential in the drive axle, a drive torque is equally vectored to wheels on left and right sides. In this way, ground adhesive force cannot be well utilized under the condition that ground adhesion is not uniform, and even slippage of the wheels and other unsteady running conditions may be easily caused on one side with low adhesion, so that the adhesive capability of a drive wheel cannot be achieved. Meanwhile, when the automobile turns at high speed, it is known from a d'Alembert's principle that, a load of the automobile may be horizontally transferred. At this moment, the load inside the automobile is decreased, and the load outside the automobile is increased. Therefore, adhesion property on the inner side is worsen, the inside wheels may slip if the torque is still equally vectored by the drive axle, and the automobile is instable. Therefore, the torque of the inside wheels of the automobile should be decreased, and the torque of outside wheels should be increased, so that lateral force margin of the inside wheels may be increased to prevent the wheels from slipping, and an additional yawing moment may be generated to the complete vehicle to facilitate vehicle turning, thereby increasing turning maneuverability and ultimate turning capability of the vehicle. At present, the technology is mainly applied to some traditional high-end internal combustion engine automobiles in a torque vectoring differential form, such as a super handling all-wheel drive system (SH-AWD) developed by Honda Company, a super active yawing control (SAYC) system developed by Mitsubishi Corporation, and the like. These torque vectoring differentials greatly increase drivebility and ultimate turning capability of the vehicle. However, the torque vectoring technology is not actually feasibly applied on the electric automobile.
In addition, since the electric automobile is generally driven to run by adopting the power assembly composed of the single motor and the drive axle or the power assembly composed of the single motor, the transmission and the drive axle, in order to meet various complicated driving conditions of the automobile, it is necessary to require that a single drive motor of the electric automobile has higher stand-by power, and then a similar phenomenon that “a big horse hauls a small carriage” in the traditional internal combustion engine automobile inevitably exists in most of the driving conditions, i.e., drive efficiency is not very high. In order to improve the drive efficiency of the electric automobile driven by a single motor, the automobile may be driven to run by adopting a primary drive motor and a secondary drive motor by virtue of a design idea of a power assembly of a hybrid electric vehicle. The primary motor provides constant power output, and the secondary motor is used for “peak-load shifting”, thereby regulating a working range of the primary motor and increasing the drive efficiency of the complete vehicle.
Therefore, in order to apply the torque vectoring technology to the electric automobile, increase the turning maneuverability and driving pleasure of the electric automobile, and increase the drive efficiency of the electric automobile by virtue of the technical advantages of the dual-motor coupling drive, a dual-motor coupling drive axle with a torque vectoring function should be designed.